Hvac filter monitoring

ABSTRACT

A method is described for identifying faults relating to an HVAC system, such a clogged filter. Sensor data is used to estimate HVAC system efficiency. Trends in system efficiency are then used to identify faults such as clogged filters. The sensor(s) can include one or more of the following types: optical sensor, temperature sensor, pressure sensor, acoustic transducer, humidity sensor, resistive sensor, capacitive sensor, and infrared sensor. The efficiency estimation can also be based on conditions external to the building, such as data from exterior sensors and/or data gathered from third parties such as government or private weather stations. The efficiency estimation can also be based on performance metrics such as the time used to reach a set point temperature. The fault identification includes filtering out non-fault related events.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/987,257 filed Jan. 10, 2011 which claims the benefit of U.S.Provisional Application No. 61/415,771 filed Nov. 19, 2010 and U.S.Provisional Application No. 61/429,093 filed Dec. 31, 2010, the entiredisclosure of which is hereby incorporated by reference, for allpurposes, as if fully set forth herein.

COPYRIGHT AUTHORIZATION

A portion of the disclosure of this patent document may contain materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND

This invention generally relates to filters in HVAC systems. Moreparticularly, embodiments of this invention relate to techniques forestimating filter status, estimating HVAC characteristics, and sensorsrelating to filters in HVAC systems.

Many HVAC systems utilize a filter for cleaning the air, which is heatedor cooled by the HVAC system. In the case of residential and/or lightindustrial buildings, these filters require cleaning or replacement,usually by the occupants, after a period of use. A dirty filterrestricts airflow through the HVAC unit, which inhibits the HVACsystem's ability to force air through the ductwork and interchange theair in the building. Often, replacement of the filter is neglected bythe user, and the performance of the system consequentially degrades.When the performance of the system degrades, not only dues the systembecome less effective in terms of the time needed to raise or lower thetemperature—leading to less comfort for the occupants, the degradedperformance can also be also a significant source of wasted energyresources and money. Thus, it is desirable to have an indication of HVACfilter status, and in particular an indication of when the HVAC filteris sufficiently clogged that it should be cleaned or replaced.

Various attempts have been discussed at determining HVAC filter status.For example, U.S. Patent Application Publication No. 2007/0228183discusses the determination of a clogged filter via airflow sensorslocated in various locations. A number of techniques rely on fan motorspeed monitoring. For example, U.S. Patent Application Publication No.2007/0234746 discusses comparing a historical calculated airflowrestriction with a current as a possible indicator of a clogged filter.The airflow restriction is calculated using a static pressure drop,which can be calculated as a function of delivered airflow, and fromsensed fan motor speed. U.S. Pat. No. 6,003,414 discusses detecting aclogged filter using static pressure, which can be derived as a functionof delivered air flow and sensing the fan motor speed. U.S. Pat. No.7,261,762 discusses detecting a clogged filter based on systemresistance determined using fan speed and power. Finally, U.S. Pat. No.7,188,482 discusses detecting faults, including filter plugging, in aduct free heat pump system known as a multi-modular split system (MMS)by utilizing various sensors located within the heating system.

Another problem that sometime arises is during installation and/or setupof a new thermostat, the HVAC system capacity may not be known by theinstaller or building occupant in the case of residential and/or lightindustrial buildings. Thus it is desirable to provide a technique ofestimating HVAC system capacity from other available information.

SUMMARY

According to some embodiments a method for identifying conditionsrelating to an HVAC system fault, such a clogged filter, is provided.The method includes receiving sensor data representing readings from oneor more sensors; estimating HVAC system performance based on thereceived sensor data; and identifying a condition relating to the HVACsystem fault based on the estimated HVAC system performance. Accordingto some embodiments, the HVAC system performance is HVAC systemefficiency. The sensor(s) can include one or more of the followingtypes: optical sensor, temperature sensor, pressure sensor, acoustictransducer, humidity sensor, resistive sensor, capacitive sensor, andinfrared sensor.

According to some embodiments the efficiency estimation is based in parton conditions external to the building, such as data from exteriorsensors and/or data gathered from third parties such as government orprivate weather stations. According to some embodiments, the efficiencyestimation is based on performance metrics such as the time used toreach a set point temperature. According to some embodiments, the faultidentification includes filtering out non-fault related events.According to some embodiments, the building in which the HVAC system isinstalled is used primarily for residential or light-industrialpurposes. According to some embodiments the identified condition, and/ora cost associated with the condition is displayed to a user.

According to some embodiments, an air filter for use with an HVAC systemis provided. The air filter includes a housing; filtering media adaptedto remove unwanted material from air passing through the HVAC system;and a sensor. According to some embodiments the air filter isdisposable. According to some embodiments, the sensor is positioned andis of a type such that an estimate of filter condition can be made basedin part on the sensor.

According to some embodiments the filter also includes one or more ofthe following: a wireless communication device adapted to transmit datafrom the sensor to a receiver; a power harvester (e.g. usingpiezoelectric elements) positioned and adapted to generate power fromair passing through the filter; and a power storage device adapted tostore power generated by the power harvester. The sensor(s) can includeone or more of the following types: optical sensor, temperature sensor,pressure sensor, acoustic transducer, humidity sensor, resistive sensor,capacitive sensor, and infrared sensor.

According to some embodiments, a method is provided for estimating HVACsystem capacity. The method includes receiving input from a userrepresenting characteristics of an air filter used in the HVAC system;and estimating HVAC system capacity based on the input received from theuser. The characteristics of the air filter can include physicaldimensions of the air filter, or the manufacturer's part numberassociated with the air filter. According to some embodiments,characteristics of the HVAC system are modeled based in part on theestimated HVAC system capacity.

As used herein the term “HVAC” includes systems providing both heatingand cooling, heating only, cooling only, as well as systems that provideother occupant comfort and/or conditioning functionality such ashumidification, dehumidification and ventilation.

As used herein the term “residential” when referring to an HVAC systemmeans a type of HVAC system that is suitable to heat, cool and/orotherwise condition the interior of a building that is primarily used asa single family dwelling. An example of a cooling system that would beconsidered residential would have a cooling capacity of less than about5 tons of refrigeration (1 ton of refrigeration=12,000 Btu/h).

As used herein the term “light commercial” when referring to an HVACsystem means a type of HVAC system that is suitable to heat, cool and/orotherwise condition the interior of a building that is primarily usedfor commercial purposes, but is of a size and construction that aresidential HVAC system is considered suitable. An example of a coolingsystem that would be considered residential would have a coolingcapacity of less than about 5 tons of refrigeration.

It will be appreciated that these systems and methods are novel, as areapplications thereof and many of the components, systems, methods andalgorithms employed and included therein. It should be appreciated thatembodiments of the presently described inventive body of work can beimplemented in numerous ways, including as processes, apparata, systems,devices, methods, computer readable media, computational algorithms,embedded or distributed software and/or as a combination thereof.Several illustrative embodiments are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive body of work will be readily understood by referring tothe following detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram of an enclosure in which environmental conditionsare controlled, according to some embodiments;

FIG. 2 is a diagram of an HVAC system, according to some embodiments;

FIG. 3 is a schematic of controller having a processing system used toestimate HVAC system conditions, such as filter status, according tosome embodiments;

FIG. 4 is a block diagram illustrating a system for identifying systemfaults, such as filter status based on changes or trends in systemefficiency, according to some embodiments;

FIG. 5 is graph plotting HVAC efficiency versus time, according to someembodiments;

FIG. 6 is a flow chart showing steps in identifying system faults,according to some embodiments;

FIG. 7 illustrates an HVAC filter having one or more built in sensors,according to some embodiments;

FIG. 8 illustrates a user interface in which the user enters an HVACfilter size, according to some embodiments;

FIG. 9 is a flow chart illustrating step in estimating HVAC capacityusing filter size, according to some embodiments; and

FIGS. 10A-10C illustrate a thermostat adapted to display informationrelating to HVAC filter efficiency, according to some embodiments.

DETAILED DESCRIPTION

A detailed description of the inventive body of work is provided below.While several embodiments are described, it should be understood thatthe inventive body of work is not limited to any one embodiment, butinstead encompasses numerous alternatives, modifications, andequivalents. In addition, while numerous specific details are set forthin the following description in order to provide a thoroughunderstanding of the inventive body of work, some embodiments can bepracticed without some or all of these details. Moreover, for thepurpose of clarity, certain technical material that is known in therelated art has not been described in detail in order to avoidunnecessarily obscuring the inventive body of work.

FIG. 1 is a diagram of an enclosure in which environmental conditionsare controlled, according to some embodiments. Enclosure 100, in thisexample is a single-family dwelling. According to other embodiments, theenclosure can be, for example, a duplex, an apartment within anapartment building, a light commercial structure such as an office orretail store, or a structure or enclosure that is a combination of theabove. Thermostat 110 controls HVAC system 120 as will be described infurther detail below. According to some embodiments, the HVAC system 120is has a cooling capacity less than about 5 tons. According to someembodiments, a remote device 112 wirelessly communicates with thethermostat 110 and can be used to display information to a user and toreceive user input from the remote location of the device 112. Accordingto some embodiments, the device 112 can be located outside of theenclosure 100.

FIG. 2 is a diagram of an HVAC system, according to some embodiments.HVAC system 120 provides heating, cooling, ventilation, and/or airhandling for the enclosure, such as a single-family home 100 depicted inFIG. 1. The system 120 depicts a forced air type heating system,although according to other embodiments, other types of systems could beused. In heating, heating coils or elements 242 within air handler 240provide a source of heat using electricity or gas via line 236. Cool airis drawn from the enclosure via return air duct 246 through filter 270,using fan 238 and is heated heating coils or elements 242. The heatedair flows back into the enclosure at one or more locations via supplyair duct system 252 and supply air grills such as grill 250. In coolingan outside compressor 230 passes gas such a Freon through a set of heatexchanger coils to cool the gas. The gas then goes to the cooling coils234 in the air handlers 240 where it expands, cools and cools the airbeing circulated through the enclosure via fan 238. According to someembodiments a humidifier 254 is also provided. Although not shown inFIG. 2, according to some embodiments the HVAC system has other knownfunctionality such as venting air to and from the outside, and one ormore dampers to control airflow within the duct systems. The system iscontrolled by algorithms implemented via control electronics 212 thatcommunicate with a thermostat 110. Thermostat 110 controls the HVACsystem 120 through a number of control circuits. Thermostat 110 alsoincludes a processing system 260 such as a microprocessor that isadapted and programmed to controlling the HVAC system and to carry outthe techniques described in detail herein.

FIG. 3 is a schematic of controller having a processing system used toestimate HVAC system conditions, such as filter status, according tosome embodiments. According to some embodiments, controller 310 iscircular shaped thermostat and has a large display area 346 which candisplay graphical and textual information to a user such as with largecentral numerals 320. User input can be received through touch screen,or with an outer rotating ring 348. A processing system 350 is used toperform much of the functionality described herein. Processing system350 includes one or more central processing units 344, storage system342, and a power supply system 340 that can include capability of usingavailable HVAC system power in the form of common wire power ifavailable or power harvesting from one or more control circuits, in thecase controller 310 is a wall-mounted thermostat that is hard-wired tothe HVAC system. According to some embodiments, power supply system 340includes one or more disposable or rechargeable batteries. According tosome embodiments, controller 310 includes one or more sensors such astemperature sensor 312, pressure sensor 314, humidity sensor 316, audiotransducer 318 and/or infrared sensor 322. According to some embodiment,one or more other types of sensors are included that may be helpful inidentifying system faults such as a particle sensor.

According to some embodiments, controller 310 is not a hard-wiredthermostat, but rather is able to control HVAC functionality, interactwith a user and make measurements from a remote location, such as atable-top, or non-hard-wired wall mount. In such cases the controller310 communicates with another controller and/or with other HVAC systemcomponents via wireless connection a low power digital radio technologysuch as Wi-Fi, or a low-rate wireless personal area network protocolsuch as ZigBee. According to some embodiments, controller 310 isequipped to communicate with other controllers or HVAC system componentswhile located outside of the building, such as using mobile phonenetwork capability or via Internet connection.

FIG. 4 is a block diagram illustrating a system for identifying systemfaults, such as filter status based on changes or trends in systemefficiency, according to some embodiments. System faults identifier 410is preferably used to model the system behavior based on various inputsand output identified system faults 440, such as HVAC filter statusinformation. System faults identifier is preferably carried out in aprocessing system such as processing system 350 as shown and describedwith respect to FIG. 3. According to some embodiments, the identifiermakes use of a system identification module such as shown and describedin co-pending U.S. patent application Ser. No. 12/881,463 entitled“Thermodynamic Modeling for Enclosures,” filed on Sep. 14, 2010(hereinafter “the '463 application”), and which is incorporated byreference herein. According to some embodiments, the system faultsidentifier 410 relies on temperature measurements 420 made within thecontroller/thermostat in order to identify a clogged filter status.According to this simple example, the system faults identifier 410 usestemperature measurements 420 and system status information, such asduring which time the various HVAC functions (e.g. heating and cooling)are in the “on” and “off” states. The identifier 410 determines trendsin HVAC efficiency and compares this with historical trends in order toidentify a likely status such as a clogged HVAC filter. In particular, aclogged filter can generally be identified by a relatively slow andsteady decline in HVAC efficiency. Other events that can significantlyeffect HVAC efficiency, such as opening and/or closing doors andwindows, duct work failures, etc. are likely to result in a more rapid,less steady, decrease (or increase) in HVAC efficiency.

According to some embodiments, the inputs 420 from sensors locatedwithin the thermostat or controller used by identifier 410 also includestatic pressure and/or humidity. Measuring static pressure can be used,in combination with other measurements, for example, to estimate airflow through certain regions of the system. According to someembodiments, other examples of sensor data that can be used byidentifier 410 include an optical sensors, a microphones or otheracoustic transducers, infrared sensors, resistivity/conductivity sensor,and particulate sensor.

According to some embodiments, inputs 422 to identifier 410 includeinformation regarding conditions outside the building, or outside theregion of space in which the environment is being controlled by the HVACsystem. For example, inputs 422 can include measurements from atemperature sensor mounted on the outside of the building which is beingconditioned by the HVAC system. In general, however the outside weathercondition information 422 can come for one or more sources. According tosome embodiments, the external conditions input 422 includes weatherconditions such as temperature, humidity, dew point, solar output,precipitation, wind and natural disasters. The external conditioninformation can be measured with sensors in, on or around the buildingand/or obtained from third party sources such as government agencies,private source and/or nearby private weather stations.

According to some embodiments, identifier 410 also relies on buildinginformation 424. The building information 424 can come from varioussources, such as building plans, which can be entered manually forexample at the time of installation or at other times. According to someembodiments, building information can come from online sources such asonline real estate databases or other databases or online services thatcollect publically available information.

According to some embodiments, identifier 410 also relies on sensorreadings 426 from other indoor locations. Examples of indoor sensors notlocated in the controller/thermostat includes sensors located in otherHVAC system components, such as one or more sensors located in the HVACfilter, as will be described in greater detail below. For example, anoptical sensor on the filter itself can be used by identifier 410.According to some embodiments, measurements of fan speed (such as bymeasuring voltage and/or current associated with the HVAC fan (such asfan 238 as shown in FIG. 2). The fan speed can be used as an indicationof air restriction due to filter clogging status. Another example ofsensors in other locations are readings from sensors located in remoteor non hard-wired locations, such as described with respect to FIG. 3.For example, there may be one hard-wired thermostat and one or moreadditional non-hard wired thermostats and communicate with thehard-wired thermostat wirelessly. By having sensor readings such astemperature or static pressure, in two or more locations, thetemperature gradient, and/or airflow (based on spatial pressuredifferential) can be estimated.

According to some embodiments the other sensor readings 426 used byidentifier 410 can include information from other household system suchas a home security system that may have information as to the openingand closing of doors and/or windows.

According to some embodiments, performance metrics 430 are calculatedand input to identifier 410. Example of performance metrics that areuseful in calculating HVAC efficiency includes the time to reach a setpoint temperature, and the amount of HVAC operation time is used inmaintaining a given temperature given certain outdoor conditions (e.g.from external conditions 422). In general the performance metrics 430are based on the amount of energy input or used to produce certainresults (i.e. system performance). For further details regarding time toreach, or maintain, set point or target temperature, see co-pending U.S.patent application Ser. No. 12/984,602 entitled “Temperature ControllerWith Time To Target Display” filed on Jan. 4, 2011, which is herebyincorporated by reference herein.

According to some embodiments, examples of other outputs 440 fromidentifier 410 include other filter status information (e.g. high levelof pollen in filter), and/or other faults such as ducting problemsand/or coolant recharge requirements.

FIG. 5 is graph plotting HVAC efficiency versus time, according to someembodiments. Curve 510 is calculated by the identifier 410 shown in FIG.4 based on one or more of the inputs as described. As can be seen inthis example, there is a steady trend in decreasing HVAC efficiency overtime. There are two regions during the time period shown in which thereis a noticeable increase in HVAC efficiency, namely at event 512 and atevent 518. The increase at event 512 is due to an event such as asignificant change in position of adjustable shutter dampers on airdiffusers, or the position of certain doors and/or windows. For example,a door or window that used be left open which caused a decrease in HVACefficiency is kept closed at event 512, thus resulting in a measurableincrease in HVAC efficiency. According to some embodiments the doorand/or window status is known from information gathered, such as from ahome security system. However, according to some embodiments, themagnitude of the increase in efficiency indicates to the identifier thatthis is not an event that is related to the status of the HVAC. Howeverat event 518, there is a significant increase in the HVAC efficiency.Additionally, the trend slope in the region 520 just before the event518 is very similar to the trend slope of the region 522 just followingthe event 518 indicates that event 518 has a high likelihood of beingrelated to HVAC filtering, and in particular is likely to represent areplacement of an old clogged filter with a new clean filter. Thus, inthis way, slow changes over time can be tracked as an indication ofinefficiency caused by the filter condition. This is in contrast to someprior techniques that detect only more serious faults and clogs of thefilter. As is discussed in further detail below with respect to FIG.10A, according to some embodiments, the filter efficiency can bedisplayed textually and/or graphically to the user.

According to some embodiments, the system queries the user as to whethera door/window position is changed, or if a filter has been replaced, sothat the system can learn the characteristics of different events. Inthis case the trained identifier can more accurately identify systemfaults.

FIG. 6 is a flow chart showing steps in identifying system faults,according to some embodiments. In step 610 the inputs as described withrespect to FIG. 4 are received by the system faults identifier. In step612 the HVAC efficiency is determined and recorded over time. Accordingto some embodiments the modeling and system identification techniquesdescribed in the '463 application are used in determining the HVACefficiency. In step 614 significant changes in HVAC efficiency areidentified, such as events 512 and 518 in FIG. 5. In step 616, afiltering process is undertaken to remove unwanted events. As mentionedabove, the filtering can be based in part on the magnitude of the changein efficiency, such that smaller events are removed. According to someembodiments, the filtering relies in part on the performance metrics asdescribed in FIG. 4, in order to distinguish different types of events.In step 618, an identified condition is displayed to the user. Forexample, if it is determined that the filter is clogged, such as just inthe region 520 of FIG. 5, a notification that the filter is clogged isdisplayed to the user. According to some embodiments, a new filter canautomatically be ordered using an on-line ordering system, when asufficiently clogged filter is determined. According to otherembodiments, a service company can be notified if a likely fault orother condition is identified that will likely require a service call.

FIG. 7 illustrates an HVAC filter having one or more built in sensors,according to some embodiments. Filter unit 710 is sized to fit as astandard replacement filter in an HVAC system. The filter unit 710includes a rigid frame 712 to fit securely in the HVAC systems and oneor more layers of v-shaped pleated filter media 714 to maximize air-flowand enhance particular capture. Two sensors 716 and 718 are provided totake a verity of readings according to various embodiments. The types ofsensors include, but are not limited to: optical, infrared, temperature,pressure, microphone or other acoustic transducer, resistive andcapacitive. According to some embodiments, more than one sensor of thesame type can be included. For example, a pressure sensor can be mountedon both sides of the filter to detect pressure drop and allowing for adetermination of air-flow. The sensors 716 and 718 are connected via oneor more wires to a controller and communication unit 720. Unit 720includes a processor, a memory, and a wireless communication system.According to some embodiments, a low power digital radio technology suchas Wi-Fi, or a low-rate wireless personal area network protocol such asZigBee is used. Power is generated from a piezo power harvesting element724 which is mounted so as to be exposed to air-flow. The power isstored in a rechargeable battery 722. According to some embodiments,transmissions are only made when sufficient power is available.According to some embodiments, the components shown in FIG. 7 aresupplied already installed in the filter unit 710, and the sensors andother components are low-cost and disposable (or recyclable) along withthe filter unit. Although a pleated type filter is shown in FIG. 7,according to other embodiments, other types of HVAC filters can beequipped as shown in FIG. 7. For example, the filter 710 can be a ringpanel/link panel design, a fiberglass filter, and/or an electrostaticfilter.

According to some embodiments, sensor data from the sensor-equippedfilter 710 is used to aid in detecting the status of the filters—such asclogging. For example, an optical sensor can be used to detect color ortone changes in the filtering media. According to another example, oneor more pressure sensors can be used to determine air flow, therebyindicating filter condition. According to some embodiments, the sensorswithin filter 710 can be used for detecting other types of faults, suchas ducting problems and/or coolant level problems.

According to the some embodiments, the sensor data from thesensor-equipped filter 710 is used for other purposes. For example,sensors on the filter 710 are located in close proximity to the furnaceand/or air conditioner unit, so they can be used to indicate how muchheating or cooling is being generated when those functions are active.This data can then be used, for example in a system identificationmodule, such as described in the '463 application. According to someembodiments, a microphone or other acoustic transducer can be used todetect other types of HVAC faults.

FIG. 8 illustrates a user interface in which the user enters an HVACfilter size, according to some embodiments. Knowing the HVAC systemheating and/or cooling capacity can be very useful for a number ofapplications. For example, for purposes of modeling of thermodynamiccharacteristics of a building having an HVAC system installed, the HVACcapacity is very useful. For further details of system identificationand thermodynamic modeling for enclosures, see the '463 application.However, a typical user of a residential and/or light-industrial HVACsystem may not know the HVAC capacity. If the user knows or can find outthe HVAC filter size, the filter size can be used to estimate thecapacity of the HVAC systems since there is in general a correlationbetween filter size and HVAC capacity. The controller 810 is of a typeas described with respect to FIG. 3, having a outer rotating ring 848and a large display area 846. The user is being asked to enter the HVACfilter size. The filter size is usually a combination of 3 dimensions.The size is entered by the user in the three fields 820, 822 and 824using the rotating ring and/or a touch screen.

FIG. 9 is a flow chart illustrating step in estimating HVAC capacityusing filter size, according to some embodiments. In step 910, the userinputs the HVAC filter size using for example, an interface as shown inFIG. 8. In step 912, optionally, building data, such as number of rooms,square footage, number of floors, etc. is downloaded, for example fromonline sources such as online real estate databases or other databasesor online services that collect publically available information. Instep 914, the HVAC capacity if estimated based on the filter size andthe building information. In step 916, the estimated HVAC capacity isused for modeling system behavior, such as is described in the '463application.

FIGS. 10A-10C illustrate a thermostat adapted to display informationrelating to HVAC filter efficiency, according to some embodiments. FIG.10A shows a thermostat 1010 that is wall mounted and has circular inshape and has an outer rotatable ring 1012 for receiving user input.Thermostat 1010 has a large frontal display area 1014. According to someembodiments, thermostat 1010 is approximately 80 mm in diameter. Theouter ring 1012 allows the user to make adjustments, such as selecting anew target temperature. For example by rotating the outer ring 1012clockwise, the target temperature can be increased, and by rotating theouter ring 1014 counter-clockwise, the target temperature can bedecreased. A selection can be made by pushing the front portion of thethermostat inward towards the wall. According to some embodiments, thelarge central numbers 1020 can be used to display the currenttemperature to users, as is shown in FIG. 10A. As described herein, thethermostat can track filter efficiency over time. The estimated filterefficiency is displayed in terms of a percentage in textual display1022, in which 100% represents a brand new clean filter. According tosome embodiments a graphical display of the filter efficiency can alsobe displayed as shown by bars 1024.

FIG. 10B shows a thermostat 1010 when the filter efficiency has droppedto 9% and the textual display 1022 is flashing to draw attention to theuser of the condition. According to some embodiments, the filterefficiency is only displayed to the user when the user asks or when thefilter efficiency drops below a certain threshold percentage.

FIG. 10C shows a thermostat 1010 displaying in textual form 1032 anestimated cost associated with the inefficiency. According to someembodiments the cost could be displayed in terms of additional energyused and or additional time required to reach a target temperature.According to some embodiments a graphical display 1034 is also used toindicate to the user the cost associated with the filter inefficiency.According to some embodiments, a textual warning 1030 can be used tonotify the use the a filter change is recommended. According to someembodiments the textual and/or graphical information shown in FIGS.10A-10C can be displayed to a user on a remote device, such as apersonal computer or a smart phone.

Although the foregoing has been described in some detail for purposes ofclarity, it will be apparent that certain changes and modifications maybe made without departing from the principles thereof. It should benoted that there are many alternative ways of implementing both theprocesses and apparatuses described herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the inventive body of work is not to be limited to the details givenherein, which may be modified within the scope and equivalents of theappended claims.

What is claimed is:
 1. An air filter for use with an HVAC systemcomprising: a housing; filtering media housed within the housing, thefiltering media being adapted to remove unwanted material from airpassing through the HVAC system; a sensor housed within the housing soas to be positioned adjacent the filtering media, the sensor being of atype that senses conditions associated with the filtering media suchthat an estimate of filter condition is determinable based at least inpart on data provided by the sensor; a wireless communication devicehoused within the housing, the wireless communication device beingadapted to transmit data from the sensor to a receiver; and a powerharvester positioned adjacent the filter and being adapted to generatepower from air passing through the filter.
 2. The air filter of claim 1,wherein data is transmitted from the sensor to the receiver via thewireless communication device only when sufficient power is availablevia the power harvester.
 3. The air filter of claim 1, wherein the powerharvester includes one or more piezoelectric elements.
 4. The air filterof claim 1, further comprising a power storage device adapted to storepower generated by the power harvester.
 5. The air filter of claim 1,wherein the sensor is of a type selected from a group consisting of:optical sensor, temperature sensor, pressure sensor, acoustictransducer, humidity sensor, resistive sensor, capacitive sensor, andinfrared sensor.
 6. The air filter of claim 1, wherein the sensor is ofa type such that an HVAC system fault is identifiable based at least inpart on data provided by the sensor.
 7. The air filter of claim 1,wherein the air filter is disposable.
 8. The air filter of claim 1,wherein the HVAC system is installed in building used primarily forresidential or light-industrial purposes.
 9. An HVAC system comprising:a thermostat device configured to receive input from a user; aprocessing system communicatively coupled with the HVAC system andthermostat, the processing system being configured to control the HVACsystem to condition a room or space within a building or structure basedon said input received from said user; and an air filter disposed withinthe HVAC system, the air filter comprising: a housing; filtering mediahoused within the housing, the filtering media being adapted to removeunwanted material from air passing through the HVAC system; a sensorhoused within the housing so as to be positioned adjacent the filteringmedia; a wireless communication device housed within the housing, thewireless communication device being adapted to transmit data from thesensor to a receiver; and a power harvester positioned adjacent thefilter and being adapted to generate power from air passing through thefilter.
 10. The HVAC system of claim 9, wherein the sensor is of a typethat senses conditions associated with the filtering media and whereinthe processing system is configured to estimate HVAC system performancebased at least in part on data received from the sensor.
 11. The HVACsystem of claim 9, wherein data is transmitted from the sensor to thereceiver via the wireless communication device only when sufficientpower is available via the power harvester.
 12. The HVAC system of claim9, wherein the power harvester includes one or more piezoelectricelements.
 13. The HVAC system of claim 9, wherein the air filter furthercomprises a power storage device adapted to store power generated by thepower harvester.
 14. The HVAC system of claim 9, wherein the sensor isof a type selected from a group consisting of: optical sensor,temperature sensor, pressure sensor, acoustic transducer, humiditysensor, resistive sensor, capacitive sensor, and infrared sensor.
 15. AnHVAC system comprising: an air filter disposed within the HVAC system,the air filter comprising: a housing; filtering media disposed withinthe housing, the filtering media being adapted to remove unwantedmaterial from air passing through the HVAC system; a sensor disposedwithin the housing and positioned adjacent the filtering media; awireless communication device disposed within the housing, the wirelesscommunication device being adapted to transmit data from the sensor to areceiver; and a power harvester disposed adjacent the air filter, thepower harvester being adapted to generate power from air passing throughthe air filter; and a processing system communicatively coupled with theHVAC system to control the HVAC system based on input received from auser, the processing system being configured to receive data from thesensor via the receiver and being further configured to: estimate aperformance of the HVAC system using the data received from the sensorand to; determine an efficiency of the air filter using the estimatedperformance of the HVAC system.
 16. The HVAC system of claim 15, whereinthe processing system is further configured to estimate a time to reacha setpoint temperature based on the efficiency of the air filter. 17.The HVAC system of claim 16, wherein the processing system is furtherconfigured to estimate a cost associated with the efficiency of the airfilter based on the time to reach the setpoint temperature.
 18. The HVACsystem of claim 17, wherein the processing system is further configuredto: generate a visual icon for a display on an electronic display of athermostat device, wherein the visual icon provides an indication of theestimated cost associated with the efficiency of the air filter; anddisplay the visual icon on the electronic display of the thermostatdevice.
 19. The HVAC system of claim 15, wherein data is transmittedfrom the sensor to the receiver via the wireless communication deviceonly when sufficient power is available via the power harvester.
 20. TheHVAC system of claim 15, wherein the air filter further comprises apower storage device that is adapted to store power generated by thepower harvester.